Epigenetic regulation of gene expression is a highly dynamic and reversible process essential to normal cellular function. However, it also contributes to human diseases, such as cancer and inflammation. Protein families that participate in epigenetic regulation include writers, which covalently modify chromatin; readers, which recognize chromatin modifications; and erasers, which remove modifications. A large volume of research in the field over the past decade has shown that many epigenetic proteins are potential druggable targets. Bromodomains, which belong to the reader's category, recognize acetylated lysine residues on histones and other proteins. Several potent, selective and cellularly active bromodomain compounds have recently been identified, increasing appreciation of the functional importance and therapeutic potential of this family. However, studies are limited and focus only on a few bromodomain subfamilies, such as the bromodomain and extraterminal (BET) proteins. There are a number of reasons that the studies have not expanded into more reader proteins; the key limitations are in both the availabilities of products and the body of knowledge for these non-BET subfamily targets. As part of the proposed project, we will systematically develop 1) complete, high-quality bromodomain proteins, 2) substrate knowledge for each target, 3) multiple assay formats for each target, 4) probe(s) for each target, 5) easy-to-use assay kits, 6) assay services for newly produced reader domains, and importantly, 7) the first drug-bromodomain interaction database, which we will build by testing each bromodomain against a large number of FDA-approved drugs and agents in clinical trials, to provide information on how these commonly used drugs and chemicals affect epigenetic activities relevant to human health.